Rock drill



Feb. 27, 1940.

H. M. STEPHENS ROCK DRILL Filed Jan. 16, 1939 M. se

IKZENTOR. 9?

Hi5 ATTO Patented Feb. 27, 1940 ROCK DRILL Henry M. Stephens, Montgomery, Va. Application January 16, 19.39, Serial Non 251,172

1 Claim.

pilots while other teeth act as reamers as well as cutters.

Another object is the provision of a drill bit of the class described and particularly suited for 15. use with pneumatic hammers, the bit being provided with air passages for directing air from the hammer into the work head of the bit for the purpose of driving finer particles away from the bit in its breaking or boring operation. it!) Another and more particular object is the provision of a rock drill or analogous device in the form of a shank. member adapted to fit into a pneumatic hammer and having a bit piece removably secured to an end thereof there being an air 25 passage through the shank member and the bit piece for directing exhaust air into the drilled hole to remove finer particulate matter, and the bit piece having a plurality of angularly arranged teeth, at least one of which is disposed in advance of the others as a pilot.

Another object is the provision of a rock drill of the class described particularly suited for use in drilling machines capable of imparting both impact and rotative movement to the bit,, the .3 drill bit being provided with a plurality of angularly disposed teeth arranged for both reaming and cutting action.

Other objects and advantages of the invention reside in certain details of construction as well no as the mode of operation of the illustrative embodiment described hereinafter in View of the annexed drawing, in which:

Fig. l is a perspective view of the pneumatic hammer employing the new bit or drill; 45 Fig. 2 is an enlarged elevational view of the bit; Fig. 3 is a fragmentary section through the bit head as seen in the direction of line 3-3 of Fig. 2; While Fig. 4 is an end view of the bit head looking in 50 the direction. of line l--4 of Fig. 3.

In the preferred form of the device shown in Fig. 2, there is provided an elongated shank member 10 of suitably hardened steel and preferably hexagonal in surface contour for greater strength, 55 there being a shoulder I I provided near the upper end, and the portion of the bit between the shoulder and the upper endconstituting aseating' portion l2 which is receivable in the chuck of the hammer.

At its lower end, the shank isuslightly reduced 5 and provided with a reverse threading l3 which runs in opposition to the normal direction of rotation of the drill in operation. The work-engaging portion of the bit is in the form of a nipple M which threads onto the threading l3 and which is provided with a plurality of cutting teeth at its free outer end. 5

The arrangement of the cutting teeth is one of the important features of the invention, there be ing a central or pilot tooth IS, the point of which lies on the center line through the drill and which extends appreciably in advance of the points of the remainingteeth. The central or pilot tooth is flanked by reaming teeth II, the points of which terminate at the outer marginal extremities of the nipple and lie behind the point of the pilot tooth. The pitch of the reaming teeth relative to that of the pilot tooth is so designed that their inner sides form obtuse angles with the sides of the pilot tooth and hence the maximum space will be left between the several teeth as the same are driven into the rock or other matter, so that broken particles may escape more rapidly whether the drillis being employed only in reciprocatory or straight concussion movement, or in a combination concussion and turning movement.

In other terms, the flanking teeth have their inner sides sloped as much as possible away from the central tooth to minimize the trapping of particles between the teeth, while at the same time providing an adequate cutting edge at the apex of each flanking'tooth. In this sense, the outer teeth are sloped a maximum away from the central tooth to provide an optimum cutting efliciency with minimized particle trapping spaces 40 between the teeth.

Another novel feature is the provision of pneumatic means for assisting in driving away broken particles from the head of the bit, this means including a concentric passage 20 leading from an entrance opening 200. atv the upper end of the shank to an exit 2% (Fig. 3) at the lower threaded end thereof, the nipple l4 being provided with a chambered portion 2| registering with the exit 201) and communicating with a plurality of angularly directed exhaust passages 22 leading from the region just above the central tooth on opposite sides of the latter.

In operation the drill H] has its upper portion [2 fitted into the chuck 30 of a hammer or drivv ing member such as the pneumatic hammer 3|, the shoulder I l limiting movement of the portion l2 into the chuck, and the hammer being of a type adapted to direct exhaust air into the entrance 20a of the air duct in the drill. The hammer is manipulated in the usual manner with the drill held in a substantially vertical position so that the pilot tooth IE will properly drive in advance of the companion teeth, as illustrated by the dotted line representation in Fig. 2. The cutting speed of this drill is greatly increased due to the action of the pilot tooth and also due to the action of the air blast in removing particles rapidly from beneath the drill head. Moreover, where the hammer or other drilling tool is of a type adapted to rotate the drill bit as well as drive the same, the teeth II also act as reamers, thus further increasing the efiectiveness of the drill and providing a substantially clean-cut hole.

The trident arrangement of the cutting formations particularly described herein has been found to be most satisfactory, but it will be appreciated that additional teeth may be arranged with respect to the pilot tooth to the same advantage.

It will be apparent that the invention provides a more efiective drill suited for either simple impact or compound impact and rotative motion and one in which the arrangement of teeth provides for greater cutting etficiency in both simple and compound motions, the pilot tooth efiecting a lead break which is immediately taken advantage of by the following flanking teeth. Where the motion is compound, rotation of the flanking teeth imparts a reaming action-which further reduces the resistance tothe drill. The angular relationshipof the several teeth permits a quicker expulsion of the particles and pulverulent matter, which is further and quickly expelled through The several objects and advantages of the in-v vention may be realized invariant forms of the particular embodiment described for purposes of illustration, and the appended claims are therefore intended to include all modifications and equivalent arrangements.

Having thus described my invention, what I claim as new and desire to protect by Letters Patent is: 1

A rock drill bit consisting of a body member of substantially cylindrical shape and provided with means at one axial end thereof adapted for attachmentto a shank member, the opposite axial end of the body member being provided with teeth lying along a line extending diametrically across said end, said other end of the body member having portionsflanking said teeth and sloping outwardly away therefrom, means providing egress for scavenging air in the region of the juncture of said teeth with said outwardly slop ing portion of the body member, and the latter being further provided with means for conducting air from said shank member through said air passage means for the scavenging air, said other outwardly sloping end portions of the body member being notched at their juncture with the cylindrical side Wall portions of said member to provide escape for scavenging air cooperably with the outwardly sloping portions of said other axial end to provide for escape of scavenging air when said teeth are substantially imbedded to the depth of their juncture with said other axial end of the body member.

HENRY M. STEPHENS; 

